Betrayal
Repeatedly throughout the text, readers are introduced to white men who "marry" their slaves. Since they are not legally permitted to marry black men, they each lead a sort of double life. They do not free their wives or children, often misleading the women to believe otherwise. This can be seen in the cases of Jefferson, Green, and Morton. Often the unfortunate women do not discover the betrayal until after their "husbands'" deaths. To make matters worse they are sold and their children enslaved. For Ellen and Jane this is too much to bear, having never experienced slavery before in their lives and finding themselves extremely ill-equipped to survive such a horrible ordeal. Green perhaps is the worst of all of them since he brings a white woman home while still "married" to Clotel. Before her eyes, he turns on their daughter, Mary, and makes her his new wife's slave. Then he sells Clotel to a plantation in Mississippi, far away so that they will never meet again.
Suffering
Slavery is a travesty. Currer, her daughters, and her granddaughters all find out the awful truth of suffering firsthand. Whether they are beaten, raped, or otherwise abused, they all suffer at the hands of their white masters. When someone is considered another person's property, their very humanity is denied. In these times there are specific laws dedicated to prevent racial mixing, so their "marriages" to their masters cannot even save them, even if they are led to believe otherwise. The highest level of preferential treatment any receive is when Althesa's daughters are given an education. Despite their unions with their masters, these women are still made to suffer immensely. In Clotel's case, she is sold by her husband and seperated from her daughter forever. When she finally accepts her fate, she commits suicide rather than live as a slave without her child a single day longer.
Racism
This seems like an obvious theme, but it manifest in unique ways in this story. To begin with, men like Jefferson prefer to use their slave women for sex rather than do the difficult work of legitimately attracting a woman. Their slaves cannot say no. These men treat Clotel and her daughters as if they are actual property, not deserving autonomy over their own bodies. In addition they make these women believe that they are their wives, but they don't really think that. Legally they are not allowed to marry any woman of African descent, so they keep their relationships secret and nonchalant, or like Morton they can pass their wife off as a white woman. All in all children are abandoned and enslaved after living their entire lives thinking they are airs to their father's fortune and freedom. Racism is a terribly destructive force in this tale which drives Clotel to kill herself in the end.
